sedimentary
Sandstone (Water-worn Cobble)
Arenite (variable composition, primarily SiO2)
Hardness: 6-7 Mohs; Color: Tan, beige, or light brown; Luster: Dull or earthy; Crystal structure: Clastic (sand-sized grains); Cleavage: None; Specific gravity: 2.2-2.8
- Hardness
- 6-7 Mohs
- Color
- Tan, beige, or light brown
- Luster
- Dull or earthy
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Physical properties
Hardness: 6-7 Mohs; Color: Tan, beige, or light brown; Luster: Dull or earthy; Crystal structure: Clastic (sand-sized grains); Cleavage: None; Specific gravity: 2.2-2.8
Formation & geological history
Formed from the accumulation and cementation of sand-sized mineral particles or rock fragments. This specific specimen was likely rounded and smoothed by high-energy water action in a river or coastal environment during the Holocene era.
Uses & applications
Used primarily as decorative landscaping, construction material (crushed stone), or as simple indoor decor and paperweights.
Geological facts
Sandstone represents approximately 20-25% of all sedimentary rocks on Earth. The smooth, oval shape of this specimen is a result of fluvial erosion, a process called 'rounding' where sharp edges are knocked off by colliding with other rocks in water.
Field identification & locations
Identify in the field by its sandpaper-like texture and visible bedding planes or layers. Commonly found in riverbeds, beaches, and desert outcrops throughout the Pacific Northwest (as suggested by the Whidbey/Anacortes context).
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